Airborne concentration of fine particles (PM2.5) hit 185 microgrammes per cubic metre in the south of Tehran and 174 in its centre on Sunday morning, local authorities said. That is far above the World Health Organization recommended maximum of 25 microgrammes per m3 over a 24-hour period.
Authorities also ordered mines and cement factories in Tehran province to close and reinforced regular traffic restrictions in the capital's centre. They called on the elderly, children, pregnant women and people with heart problems to stay indoors.
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